Disc drives are common data storage devices. A typical disc drive includes a rigid housing that encloses a variety of disc drive components. The components include one or more rotating discs having data surfaces that are coated with a medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor that causes the discs to spin and the data surfaces of the discs to pass under respective aerodynamic bearing disc head sliders. The read/write heads carry transducers, which write information to and read information from the data surfaces of the discs.
Typically, the read/write head includes an inductive recording or write element for generating a magnetic field that aligns the magnetic moments of the data surfaces to represent desired bits of data. The write element includes a magnetic core having a write gap to record magnetic transitions in the magnetized medium surface of a disc. The core is magnetically coupled to a conductive coil. Electrical current flows through the conductive coil during write operation and generates magnetic flux in the core to record transitions in the magnetic surface coating of the rotating disc or other medium. The magnetic core includes a main pole and a return pole, wherein each pole has a corresponding pole tip adjacent a surface opposing the storage medium. In a write head, for example, the pole tips are positioned on an air-bearing surface (ABS) of the slider. The distance between the main pole tip and the return pole tip is the write gap or gap length.
The read head includes a magnetoresistive read sensor that is adapted to read magnetic flux transitions recorded to data tracks on the medium which represent the bits of data. The magnetic flux from the recording medium causes a change in the electrical resistivity of the read element, which can be detected by passing a sense current through the read element and measuring a voltage across the read element. The voltage measurement can then be decoded to determine the recorded data.
With the continuing need to meet the never ending demands for higher disc drive storage capacity, the read/write head to media nominal spacing has been decreasing to pursue greater areal densities. Thermal pole tip protrusion can be a significant percentage of the total nominal spacing between the head and disc. Thus, pole tip protrusion can effect the write performance of the disc drive. For example, the plurality of circular, concentric data tracks on the magnetic medium is divided into data sectors. As electrical current initially conducts through the conductive coil during write operation, the core is heated. The heating of the core results in thermal expansion of the pole tips. As a result of thermal expansion, the pole tips begin to protrude and push the write element closer to the surface of the disc, which, when thermally stabilized, result in a more efficient write process. However, there is less pole tip protrusion while the first few data sectors are written than in later data sectors when the temperature of the write element has stabilized. The problem may be exacerbated in a low temperature ambient environment because colder ambient temperatures cause the pole tips to recess away from the disc such that the head to media spacing is even greater in the first few data sectors.